Triploidization of brown trout (Salmo trutta) by heat shocks

This study was made to optimize heat shock conditions for producing triploidy in the brown trout, Salmo trutta. Heat shock at 29°C for 10 min duration, initiated between 5 and 45 min after insemination, gave high frequencies of triploid embryos (77-91%) as assessed by chromosome observation. Shocks initiated between 90 and 260 min following insemination had no effect on polyploidization. Other groups heat shocked at 29°C for 5-15 min duration initiated 10 min after insemination resulted in moderate rates of triploidy (50-63%). A high temperature shock of 32°C for 6 min duration gave 100% triploidy but a lower temperature shock of 26°C, even for 30 min duration, had only a moderate effect (57%). Rates of hatching were generally decreased in the groups giving moderate to high frequencies of triploidy. In most treated lots haploid embryos were observed and were considered to be a cause of decreased survival.